The present invention relates to automatic injectors for delivering medicament to an injection site. In particular, the present invention is directed to an automatic injector assembly for quickly combining a liquid material with a dry material to form a liquid medicament for delivering the medicament to an injection site. In accordance with the present invention, the automatic injector assembly includes a separation filter assembly that keeps the liquid material separated from the dry material until the automatic injector assembly is activated.
An automatic injector is a device for enabling an individual to self-administer a dosage of medicament into his or her flesh. The medicament is usually stored in liquid form. The advantage of automatic injectors is that they contain a measured dosage of a liquid medicament in a sealed sterile cartridge and can be utilized for delivering the medicament into the flesh during emergency situations. Another advantage of automatic injectors is that the self-administration of the medicament is accomplished without the user initially seeing the hypodermic needle through which the medicament is delivered and without having the user to manually force the needle into his or her own flesh.
There are drawbacks associated with the storage of medicament in liquid form. Some medicaments are not stable in liquid form. Furthermore, some liquid medicaments typically have a shorter shelf life than their solid counterparts. Others have developed automatic injectors that store the medicament in solid form and a liquid injection solution. These injectors, disclosed for example in U.S. Reissue Pat. No. 35,986, entitled xe2x80x9cMultiple Chamber Automatic Injector,xe2x80x9d (the disclosure of which is incorporated herein specifically by reference), however, require the user of the injector to expedite dissolution of the solid component by manually shaking the liquid component and the solid component immediately prior to injection. This increases the time needed to administer a dose of medicament. Furthermore, the improper mixing of the medicament with the liquid injection solution may release an insufficient dose of medicament. There is a need for an automatic injector that stores medicament in solid form that does not require manual premixing by the user. Furthermore, rapid delivery of the medicament is needed for emergency medical situations (e.g. nerve gas and chemical agent poisoning).
It is therefore an object of the present invention to provide an automatic injector device that stores medicament in a solid form for increased shelf life.
It is another object of the present invention to provide an automatic injector device that automatically mixes a solid medicament with a liquid injection solution upon activation.
It is another object of the present invention to provide an automatic injector device having a separation filter assembly that separates the solid medicament from the liquid injection solution until the injector is activated.
It is another object of the present invention to provide an automatic injector device having a filter assembly that provides for a more laminar flow of the liquid injection solution into the dry medicament to assist in the dissolution of the dry medicament into the liquid injection solution.
It is another object of the present invention to provide a wet/dry automatic injector device with a solid medicament support within the device to prevent the passage of undissolved solid medicament to the needle assembly of the injector assembly thereby preventing blockage of the needle.
Additional objects and advantages of the invention are set forth, in part, in the description which follows, and, in part, will be apparent to one of ordinary skill in the art from the description and/or practice of the invention.
In response to the foregoing challenges, applicants have developed an innovative automatic injection device having both wet and dry storage compartments. The present invention is directed to an automatic injection device containing a pre-loaded charge of medicament for automatically self-administering the medicament upon actuation thereof. The automatic injection device includes a housing assembly having an interior chamber, a filter assembly, an activation assembly and a needle assembly. In accordance with the present invention, the interior chamber may include a dry compartment for storing a predetermined dry charge of dry medicament therein, and a wet compartment for storing a predetermined amount of liquid injection solution therein.
The filter assembly is positioned between the dry compartment from the wet compartment. The filter assembly creates a laminar fluid flow of liquid injection solution as the solution passes from the wet compartment to the dry compartment. This improves dissolution of the dry medicament in the liquid injection solution.
The automatic injector in accordance with the present invention includes a plunger assembly positioned adjacent the filter assembly. The plunger assembly is adapted to prevent the transfer of the liquid injection solution from the wet compartment to the dry compartment prior to pressurization of the liquid injection solution within the wet compartment. In accordance with one embodiment of the present invention, the plunger assembly may include a passageway for transferring the liquid injection solution from the wet compartment to the dry compartment and a membrane assembly for preventing the transfer of the liquid injection solution from the wet compartment to the dry compartment prior to the pressurization of the liquid injection solution within the wet compartment. The membrane is designed to rupture upon pressurization of the wet compartment. In accordance with another embodiment of the present invention, the plunger assembly is adapted to moves from a first position to a second position during the pressurization of the liquid injection solution within the wet compartment. This movement opens a fluid passageway between the plunger assembly and the interior chamber to permit the passage of the liquid injection fluid from the wet compartment to the dry compartment.
The activation assembly pressurizes the liquid injection solution in the wet compartment, which causes the liquid injection solution in the wet compartment to be transferred to the dry compartment. The dry medicament dissolves in the liquid injection solution as the liquid injection solution passes through the dry compartment. It is contemplated that at least a portion of a plunger assembly of the activation assembly may contact the plunger assembly adjacent the filter assembly, which moves the filter and plunger assembly towards the needle assembly to force the remaining liquid injection solution and the dry medicament through the needle assembly.
The automatic injection device may further include a dry medicament support structure located within the interior chamber. The support structure prevents undissolved dry medicament from entering the needle assembly.